Matrix key input interface

摘要

A matrix key input interface has key common signal lines and key data signal lines wired in a matrix and key switches disposed at positions where the key common signal lines intersect the key data signal lines. The key data signal lines are periodically monitored while key scan signal is not output to any of the key common signal lines. Based on the results of monitoring, an earth fault is detected in key common signal lines or key data signal lines.

主权项

1. A matrix key input interface with a sink key matrix circuit, the sink key matrix circuit comprising:
m (m is a natural number) key common signal lines and n+1 (n is a natural number) key data signal lines wired in a matrix; and m×n key switches connected between the m key common signal lines and a first to an n-th key data signal lines, the key common signal lines intersecting the key data signal lines, wherein a sneak preventing diode is connected between the n+1-th key data signal line and each of the m key common signal lines, the matrix key input interface further comprising: a monitoring unit that periodically monitors all of the n+1 key data signal lines while key scan signal is not output to any of the m key common signal lines; and a detection unit that detects an earth fault when any of the key data signal lines is at an L level while the key data signal lines are being monitored by the monitoring unit.